roller bearing

roller bearing (plural roller bearings)

2. A bearing in which the load is carried by round (e.g. cylindrical or spherical) elements (rollers).

   Hypernyms: bearing < component, part

   Hyponyms: ball bearing, needle bearing

   • 1952 February, “New Locomotives for the Gold Coast [now Ghana]”, in Railway Magazine, page 74:

     Thirty mixed-traffic 4-8-2 locomotives recently completed by the Vulcan Foundry Limited for the 3 ft. 6 in. gauge Gold Coast Government Railway have all their axles, big ends, and coupling and eccentric rods fitted with British Timken roller bearings.

   • 1959, edited by David P. Morgan, Steam's Finest Hour, Kalmbach Publishing Co.:

     In 1930 the proposal of placing all axles of a steam locomotive on roller bearings was viewed so suspiciously that the Timken Roller Bearing Company couldn't even obtain permission to equip an existing engine at its own expense. (It ended up buying a demonstrator loco and equipping that with roller bearings instead.)

   • 1961 November, “Talking of Trains: The roller-bearing A1s”, in Trains Illustrated, page 643:

     The five roller-bearing A1s are now averaging 120,000 miles between shopping; this figure is an improvement of about 50 per cent on the norm of other ex-L.N.E. Pacific types.

   2. (especially) Such a bearing with cylindrical rollers rather than spherical ones (balls).

      Hyponym: needle bearing

      Coordinate term: ball bearing

By an arbitrary but widely upheld idiomatic convention, precise usage in mechanical industries often holds roller bearing and ball bearing to be coordinate terms under the hypernym of rolling-element bearing, in which case rollers that are spherical are excluded as referents of the word roller and are instead called balls.